Clay-binder and process of making same.



UNITED s A'rEs PATENT ora ion- HENRY L. KOHLER, OF ST. LOUIS, MISSOURI.

CLAY-BINDER AND PROCESS OF MAKING SAME.

No Drawing.

To all whom it may concern:

Be it known that I, HENRY L. KonLnn, a

citizen of the United States, residing at St.

ticity of clays is their capacity to be molded into any required formwithout loss of cohesion, and depends in a large measure not only on thechemically combined and hygroscopic water contained in the clay, but onthe fineness of the clay, and to some extent on the amount of aluminaentering into its composition. This plasticity however disappears afterbaking even where the clay is powdered very finely. Clay should howeverpossess sufiicient bonding properties to permit not only of molding, butto allow for the necessary shrinkage in the baking operation withoutcracking or splitting. This precaution against cracking is all the morenecessary in the case of fire brick, which as a rule is subjected torapid alternations or changes of temperature while'in service. In

'the manufacture of fire brick this cracking or splitting is avoided byfirst tempering the raw clay by exposure to the atmosphere beforemolding the same into bricks and also mixing it with other materialssuch as ground burnt fire clay, or grog (old groundup bricks). Unlessthe clay to which "the burnt fire clay or grog is to be added hassutficient bonding properties it will not hold any considerablepercentage of these materials and hence can not be used to advantage inthe molding andburning operations in the manufacture of fire brick. Thepresent invention is directed to the treatment of nonplastic clays ingeneral, and to flint clays in particular, the object sought being notonly to impart plasticity to the clay, but to impart thereto thenecessary bonding properties which a fire clay should possess to beproperly molded, and amalgamated Witlr grog and-burnt fire clay toinsure the production, --"of a serviceable non-fusible fire brick. "Aswell understood in the art, sand (SiO as an impurity influences the'plasticity of clays unfavorably, whereas iron and lime alter it verylittle; and while a non-plastic clay such as flint-clay is on theSpecification of Letters Patent.

Application filed March 24, 1919.

As well'understood in the art, the 'plas- Patented Au 12, 1919.

Serial No. 284,854.

less free silica, the pressure of free silica therein destroys thebonding properties so essential to perfect molding and subsequentburning or baking. I have discovered that a basic salt of aluminum addedto, or formed in the clay as a result of chemical reaction between thealuminum silicate of the clay and an aluminum salt of a mineral acid, orfree acid, added to the clay in the wet state, not only forms anadmirable binder for the clay so as to permitready molding thereof andamalgamation with grog or burnt fire clay, but permits baking of theclay without danger of cracking or splitting. The basic salt referred tooperates as a binder for the clay during the tempering and moldingstage, said salt being gradually converted into the oxid (and silicate)during the burning or. baking stage without losing its effectiveness asa binder. Besides acting as a binder it adds alumina to the clay therebymaking a more neutral material, the alumina serving to lower, orentirely eliminate the'free silica present by converting't-he latterinto the silicate of aluminum. The manner of forming the binder in theclay mass maybe described as follows:

For our purpose we may assume thatthe non- 'same with the clay. Thealuminum sulfate combining with the water crystallizes and in socrystallizing acts as a'temporary binder, rendering the mass cohesive.The mixture is allowed to remain at ordinary atmospheric temperature(-70 degrees Fahr.)

for a'sufiicient length of time to bring about the conversion of thealuminum sulfate into a basis salt of aluminum, by the aluminum silicateof the clay, the reaction being substantially and approximately asfollows:

In the burning or bakingoperation (where the material is formed intobricks) these basic sulfates are converted into oxids, and a portion ofthe latter are converted into silicates either by the silicic acid setfree in the reaction betweenthe clay and aluminum salt, or 'by said acidand any free silica which may be present in the clay. At the bakingtemperature (red'heat) the sulfur radical (S0 is simply driven off andthe oxid of aluminum (A1 0,) remains behind.

A portion of this oxidby reaction with the silicic acid, or free s1hcaof the clay, or both, forms a silicate as follows:

the basic salts of aluminum serve as a binder for the clay while thelatter is being molded, thereby overcoming the non-plasticity of theoriginal body of clay (flint or non-plastic clay); and that the oxid andsilicate of aluminum resulting from the decomposition of the basicsulfates and the conversion of a portion thereof into the silicate athigh temperature, serve'in turn as a binder for the baked or burnt clay,the danger of cracking or splitting being thus wholly eliminated.

lVhile I have here described the use of aluminum sulfate as the reagentto be added to the original clay mass to form the basic salts, it is tobe understood that I do not wish to be restricted to this particularreagent. I may for example, where the clay is very pure, start withsulfuric acid, which, when added to the clay, converts the silicate ofaluminum into the sulfate, this in turn by further reaction forming thebasic sulfate. I may too, start with ammonium sulfate with like results.In fact any mineral acid or salt thereof capable of setting free thesilicic acid of the aluminum silicate of the clay may be used in lieu ofaluminum sulfate. An example of such equivalent would be aluminumnitrate or nitric acid. In practice, the aluminum sulfate to 5 per cent.by weight) or its equivalent is added to a mixture of substantially twoparts of finely ground burnt fire clay, or grog, and one part of thefinely ground raw clay, this proportion making an excellent fire brick,though I may use other mixtures ample, as the quantity of salt orequivalent reagent used will depend on the fineness and degree ofplasticity of the clay. The finer and less non-plastic clays require asmaller quantity of binder reagent than the coarser and more non-plasticvariety. In the case of fine clays anywhere from one half to two percent. of reagent will suffice; for coarser grades of clay a largerpercentage of reagent is needed.

In the examples above cited the basic aluminum salt is formed byreaction within the mass of clay treated; but it is entirely within thescope of my invention to form such basic salt apart from the clay in anymanner known to the art, and then add the salt (dissolved in water) tothe clay, the basic salt whether added to the clay from without orwhether formed by reaction in the body of the clay serving as a binderfor the clay and rendering the same plastic for molding purposes.

The basic salt binder need not necessarily be exclusively a salt ofaluminum, that is to say, the base of the compound employed as thereagent need not necessarily contribute the element aluminum to thebasic salt resulting from the reaction, it being possible to employ areagent having a base other than aluminum. If for example we add to theclay the required quantity or percentage of zirconium sulfate, the finalreaction will result in a binding material comprising a mixture of thebasic sulfates of zirconium and aluminum, the reason therefor being thatthe affinities of zirconium and aluminum for the sulfur radical areabout the same, and their normal sulfate salts are isomorphous. Thefollowing is substantially the reaction when zirconium sulfate isemployed as the reagent The foregoing example is cited merely to showthat the portion of the basic salt derived from the reagent added to thecharge of clay may have a base other than aluminum, and still serve itspurpose as a binder. Of course Zirconium sulfate would hardly do inpractice owing to the high cost of this reagent, but its employmentfalls within the scope of my invention.

The binder here described is not restricted in its application to claysor silicates of aluminum, as the same may be applied to argillaceousmaterial such as bauxite or the hydrate of aluminum (Al O,,.2H. ,O).When added to bauxite. the aluminum sulfate (or its equivalent) likewiseforms a basic salt or salts with the aluminum hydrate, serving as abinder for the bauxite at ordinary tern peratures, the said binder beingconverted into an oxid of aluminum when the bauxite is baked, a portionof the oxid combining with the free silica ofthe bauxite when present(it usually is) and forming a silicate of aluminum.

To properly function as a binder-forming reagent, the acid of thecompound added to the clay, be such acid free or in combination, must besuificiently strong to dissociate the silicic acid from the aluminumsilicate of the clay; otherwise the basic salts of the acid of thereagent will not form.

For this reason organic acids or salts of organic acids (for exampleacetic acid or The term clay as used herein, and par-- ticularly in theclaims, is to-be given its broadest interpretation, the same includingnot'only the silicates of aluminum, but the oxids and hydrates as Well,or any combi nation of the three.

Having described my invention What I claim is 1. A body of clay having abinder comprising a basic sulfate of aluminum generated Within the massof the clay.

2. In the treatment of clays, the process consisting in mixing With thefinely divided moist clay a quantity of a reagent containing an acidcapable of dissociating the silicic acid from the aluminum of the clay,and continuing the reaction to permit the formation of the basicsalts'of aluminum in the clay mass.

3. In the treatment of clays, the process consisting in mixing with thefinely divided Wet clay a quantity of a reagent containing av mineralacid to decompose the silicate of aluminum of the clay, and continuingthe reaction to form basic aluminumsalts of said acid in the clay mass.

4. In the treatment of clays, the process consisting in mixing with thefinely divided moist clay a quantity of a metal sulfate capable ofdecomposing the aluminum silicate of the clay, and continuing thereaction to form basic aluminum sulfate in the clay mass.

5. In the treatment of clays, the process consisting in mixing with thefinely divided moist clay a quantity of aluminum sulfate to decomposethe aluminumsilicate of the clay, and continuing the reaction to formbasic aluminum sulfate in the clay mass.

6. In the treatment of clays, the process consisting in mixing with thefinely divided moist clay a quantity of a reagent contain ing an acidcapable of dissociating the silicic acid from the aluminum ofthe clay,

containing the reaction to form basic aluminum salts of the reagentacid, and heating the clay to convert said basic salts into the oxid ofaluminum.

7. In the treatment of clays, the process consisting in mixing With thefinely divided clay apredetermined quantity of a reagent containing anacid capable of dissociating the silicic acid from the aluminum of theclay, continuing the reaction to form basic aluminum salts of thereagent acid, heating the clay to convert said basic salts into aluminumoXid and causing said oXid or a portion thereof to combine with thesilicic acid or free silica present to form a silicate of aluminum.

8. In combination with a mass of moist non-plastic clay, a biddercomprising a basic salt of an acid capable of; decomposing the aluminumsilicate of the clay, said salt being convertible into an oxid servingas a binder for the clay at baking temperature.

9. In combination with a mass of moist non-plastic clay, a bindercomprising a basic sulfate of aluminum.

10. In the treatment of clays containing free silica, the processconsisting in adding to the finely divided moist clay a suitable Qquantity of a salt binder containing an acid capable of decomposing thesilicate of aluminum of the clay, burning or baking the clay to convertthe binder into an oxid, and causing the oXid to combine with the freesilica and form a silicate of the base of said salt;

11. A clay moistened to be molded comprising a silicate of aluminum, anda binder of a basic salt of aluminum.

12. In combinationwith a body of clay, a binder comprising a basic saltof aluminum.

13. In combination with a body of clay,

a binder comprising a basic sulfate of alu- V minum. a

In testimony whereof I affix my signature, 1n presence of two witnesses.

HENRY L. KOHLER. Witnesses EMIL S'roREK, 'ELSE M. SIEGEL.

Correction in Letters Patent No. 1,312,853.

It is hereby certified that in LettersPatent No. 1,312,853, grantedAugust 12, 1919,

upon the application of Henry L. Kohler, of St. Louis, Missouri, for animprovernent in Clay-Binders and Processes of Making Same, an errorappears in the printed specification requiring correction as f011ows:Page 1, line 57, for the word pressure read presence; and that the saidLetters Patent should be read with this correction therein that the samemay conform to the record of the case in the Patent Ofiice.

Signed and sealed this 21st day of October, 1)., 1919.

[SEAL] i M. H. COULSTON,

Acting Commissioner of Patents.

